1. Field of the Invention
The invention concerns in general terms lighting and/or signaling devices intended to be mounted in motor vehicles. More particularly, the invention concerns lighting and/or signaling devices for a motor vehicle comprising at least one power light emitting diode light source and other means able to constitute one or more heat sources of such a nature as to affect the thermal environment of the power light emitting diode light source.
2. Description of the Related Art
Recent technological developments in the field of white power light emitting diodes make more and more probable a rise in power in the use of these light sources for performing lighting and signaling functions in a vehicle.
With regard to technical performance, power light emitting diodes, referred to as “power LEDs”, have undeniable strengths making them particularly attractive in a certain number of applications. With regard to their service life, their efficiency and their shape factor, power LED diodes have a great advantage in particular compared with more traditional light sources such as filament lamps.
The integration of power LED diodes in headlights and signaling lights does however pose difficulties and new constraints relating to the necessity for efficient thermal management in a relatively confined environment represented by the internal volume of a headlight or signaling light. These thermal management constraints are particularly difficult to overcome in the case of a headlight, in particular because of the location thereof partly in the engine compartment of the vehicle and the lighting powers concerned.
This efficient thermal management is necessary in the case of power LED diodes because of the fact that the maximum nominal values of the junction temperatures thereof, around 150° C., are relatively low in the context of automobile lighting/signaling applications. This is because it is frequent for an internal ambient temperature of 90 to 100° C. to be reached.
Current technical solutions consist of mounting the substrates supporting the power LED diodes on one or more aluminum heat sinks in close thermal contact with them. A forced circulation of air by means of a fan is also sometimes introduced so as to improve the thermal dissipation. These known solutions may lead to heat sinks of significant volume and weight that make it tricky to design modern lighting/signaling devices in which new functions of the AFS type are to be installed. AFS is the abbreviation of the English term Advanced Front Lighting System, and groups together, in recent European regulations, a certain number of new functions such as bending dipped beam, also referred to in English as DBL, standing for “dynamic bending light”, or motorway beam, referred to in English as “motorway”.
These new functions may lead to adding supplementary light sources that constitute as many close heat sources having a substantial impact on the junction temperature of the power LED diodes.
Moreover, without going here into the details of the normal drawbacks relating to the weight of equipment installed in a motor vehicle, let us note particularly that the inclusion of heat sinks substantially increases the mechanical inertia of the parts supporting the LED diodes, knowing that the latter are liable to move in rotation dynamically in the context of a bending dipped lighting function (DBL, standing for “dynamic bending light” in English).